Istanbul is the largest city in Turkey, constituting the country's economic, cultural, and historical heart. Istanbul is a transcontinental city in Eurasia, with its commercial and historical centre lying on the European side and about a third of its population living on the Asian side of Eurasia. With a population of 14.4 million, the city forms the largest urban agglomeration in Europe as well as the largest in the Middle East, and the sixth-largest city proper in the world. Istanbul's vast area of 5,343 square kilometers (2,063 sq mi) is coterminous with Istanbul Province, of which the city is the administrative capital. Istanbul straddles the Bosphorus strait in northwestern Turkey, between the Sea of Marmara and the Black Sea.